main() {
  // 变量声明
  var a = 10;
  print(a);
  a = 20;
  print(a);
  //常量声明
  const BASE_URL = 'https://www.baidu.com';
  print(BASE_URL);

  //变量的类型
  var age = 18;
  print(age);
  age++;
  print(age);

  //变量的类型
  var name = true;
  print(name);
  name = false;
  print(name);

  const BASE_URL2 = 'http://www.itcast.cn';
  print(BASE_URL2);
}
